1. Field of the Invention
The present invention relates to an ink-jet printhead and a method for manufacturing the same, and more particularly, to an ink-jet printhead having an improved structure in which a heater is formed by connecting conductors with a plurality of conductor connection layers, and a method for manufacturing the same.
2. Description of the Related Art
In general, ink-jet printheads are devices for printing a predetermined color image by ejecting small volumes of droplets of printing ink at desired positions on a recording sheet. According to the ink ejection mechanism, these ink-jet printheads are divided into ink-jet printheads using a thermal driving method, ejecting ink droplets by the expansion force of bubbles generated in ink by a heat source, and ink-jet printheads using a piezoelectric driving method, ejecting ink droplets by the pressure applied to ink due to the deformation of a piezoelectric body.
Hereinafter, the ink ejection mechanism in the thermal ink-jet printheads will be described in greater detail. When a pulse current flows through a heater formed of a resistance heating material, heat is generated in the heater, and ink adjacent to the heater is heated to about 300° C. At such a temperature, the ink boils, and bubbles generated in the ink, expand, and apply pressure to an inside of an ink chamber filled with ink. As a result, ink in the vicinity of a nozzle is ejected in droplets through nozzles to the ink chamber.
FIG. 1 is a cross-sectional view illustrating a vertical structure of a conventional ink-jet printhead disclosed in U.S. Pat. No. 6,293,654. Referring to FIG. 1, the conventional ink-jet printhead includes a base plate 10 formed by a plurality of material layers stacked on a substrate 11, a barrier wall 20 formed on the base plate 10 and defining an ink chamber 22, and a nozzle plate 30 stacked on the barrier wall 20. Ink is filled in the ink chamber 22, and a heater 13 heating ink and generating bubbles, is installed under the ink chamber 22. The ink chamber 22 is connected to an ink passage (not shown) forming a path supplying ink to an inside of the ink chamber 22. A plurality of nozzles 32, through which ink is ejected, are in the nozzle plate 30 in correspondence with the ink chamber 22.
The vertical structure of the ink-jet printhead described above is described below in greater detail.
An insulating layer 12, for insulation between the heater 13 and the substrate 11, is on the substrate 12, formed of silicon. The insulating layer 12 is formed by depositing a silicon oxide layer on the substrate 11. The heater 13, heating ink in the ink chamber 22, and generating bubbles, is formed on the insulating layer 12. The heater 13 is formed, for example, by depositing thin-film tantalum nitride (TaN) or thin-film tantalum-aluminum (TaAl) on the insulating layer 12. A conductor 14, applying a current to the heater 13, is formed on the heater 13. The conductor 14 is made of aluminum (Al) or an aluminum (Al) alloy, for example. The conductor 14 is formed by depositing Al on the heater 13 to a predetermined thickness, and patterning Al in a predetermined shape.
A passivation layer 15, for passivating the heater 13 and the conductor 14, is formed on the heater 13 and the conductor 14. The passivation layer 15 prevents the heater 13 and the conductor 14 from oxidizing, or directly contacting, ink, and is formed by depositing a silicon nitride layer. In addition, an anti-cavitation layer 16, on which the ink chamber 22 is to be formed, is formed on the passivation layer 15. The top surface of the anti-cavitation layer 16 forms the bottom surface of the ink chamber 22, thereby preventing the heater 13 from damage due to a high atmospheric pressure generated when bubbles in the ink chamber 22 are expelled. The anti-cavitation layer 16 is usually made of thin-film tantalum (Ta).
The barrier wall 20, forming the ink chamber 22, is stacked on the base plate 10 formed of a plurality of material layers stacked on the substrate 11. The barrier wall 20 is formed by coating a photosensitive polymer on the base plate 10 by lamination, including heating, pressing, and squeezing, and by patterning the photosensitive polymer. In this case, the coating thickness of the photosensitive polymer depends on the height of the ink chamber 22 required in a volume of ejected ink droplets.
The nozzle plate 30, in which the nozzles 32 are formed, is stacked on the barrier wall 20. The nozzle plate 30 is made of polyimide, or nickel, and attached onto the barrier wall 20 using adhesion of the photosensitive polymer forming the barrier wall 20.
However, in the ink-jet printhead having the above structure, the heater 14, for generating a thermal energy, is made of a metallic material having a high resistance of about 30 ohm/square. On the other hand, the conductor 14 applying current to the heater 13 is made of a metallic material having resistance much lower than 30 ohm/square. Thus, in the ink-jet printhead described above, the conductor 14 and the heater 13 cannot be made of the same metallic material.